This invention relates to electrostatic precipitators and, more particularly, to a new, improved and more efficient wet electrostatic precipitator.
Electrostatic precipitators are used for air pollution control, gas cleaning, separation, and particle removal. The fluid, such as a gaseous medium, flows under pressure between collection plates and discharge electrodes which latter are adapted to produce a corona and an electrostatic field when a sufficiently high voltage is applied thereto. Preferably the voltage is negative to produce a negative corona effect and an ionization.
Both positive and negative ions are generated in the corona, with the positive ions remaining on the negatively charged discharge electrode while the negative ions pass over to the grounded collection plates along the lines of force of the electrostatic field extending therebetween. The particles to be precipitated intercept the negative ions, are charged thereby, and are attracted to the adjacent collection plate. The fluid leaving the electrostatic precipitator moves on to recovery or exhaust.
Various means are utilized to periodically remove particles from the collection plates, among which may be mentioned intermittent spraying of the collection plates with water and rapping said plates with vibrators. However, although electrostatic precipitators of the mentioned type are highly efficient, an amount of charged and neutral particles generally escapes from the downstream side of the stack of alternating collection plates and discharge electrodes. Such particles either never reached the collection plates or were reentrained from the collection plates by the fluid flowing over the collection plates. These particles move with the fluid and experience has shown that the charged particles partially attach themselves to pipes and walls downstream of the collection plate area. Certain tarry precipitates adhere to the collection plates and cannot be removed by intermittant sprays or by rapping. The accummulation of such precipitates causes breakdown of the precipitator necessitating dismantling and manual cleaning thereof. Further, a dry electrostatic precipitator will not remove gases from the fluid medium. One way of assuring substantially complete collection and removal of all the particles and selective removal of gaseous contaminants from a flowing stream of fluid medium or the like without accummulation of precipitate on the collection plates is by using a so-called wet electrostatic precipitator (WEP).